Put cprng sysctls into subr_cprng.c. Also, make sysctl_prng static
in subr_cprng and get rid of SYSCTL_PRIVATE namespace leak macro.
Fixes ping(8) when run against a standalone rump kernel due to appearance
of the kern.urandom sysctl node (in case someone was wondering ...)

Replace consttime_bcmp/explicit_bzero by consttime_memequal/explicit_memset.
consttime_memequal is the same as the old consttime_bcmp.
explicit_memset is to memset as explicit_bzero was to bcmp.
Passes amd64 release and i386/ALL, but I'm sure I missed some spots,
so please let me know.

Convert the entropy pool framework from pseudo-callout-driven to
soft interrupt driven operation.
Add a polling mode of operation -- now we can ask hardware random number
generators to top us up just when we need it (bcm2835_rng and amdpm
converted as examples).
Fix a stall noticed with repeated reads from /dev/random while testing.

Re-fix 'fix' for SA-2013-003. Because the original fix evaluated a flag
backwards, in low-entropy conditions there was a time interval in which
/dev/urandom could still output bits on an unacceptably short key. Output
from /dev/random was *NOT* impacted.
Eliminate the flag in question -- it's safest to always fill the requested
key buffer with output from the entropy-pool, even if we let the caller
know we couldn't provide bytes with the full entropy it requested.
Advisory will be updated soon with a full worst-case analysis of the
/dev/urandom output path in the presence of either variant of the
SA-2013-003 bug. Fortunately, because a large amount of other input
is mixed in before users can obtain any output, it doesn't look as dangerous
in practice as I'd feared it might be.

Fix a security issue: when we are reseeding a PRNG seeded early in boot
before we had ever had any entropy, if something else has consumed the
entropy that triggered the immediate reseed, we can reseed with as little
as sizeof(int) bytes of entropy.

Don't wait until the pool *fills* to rekey anything that was keyed with
insufficient entropy at boot: key it as soon as it makes any request after
we hit the minimum entropy threshold.
This too should help avoid predictable output at boot time.

Address multiple problems with rnd(4)/cprng(9):
1) Add a per-cpu CPRNG to handle short reads from /dev/urandom so that
programs like perl don't drain the entropy pool dry by repeatedly
opening, reading 4 bytes, closing.
2) Really fix the locking around reseeds and destroys.
3) Fix the opportunistic-reseed strategy so it actually works, reseeding
existing RNGs once each (as they are used, so idle RNGs don't get
reseeded) until the pool is half empty or newly full again.

Fix LOCKDEBUG problems pointed out by drochner@
1) Lock ordering in cprng_strong_destroy had us take a spin mutex then
an adaptive mutex. Can't do that. Reordering this requires changing
cprng_strong_reseed to tryenter the cprng's own mutex and skip the
reseed on failure, or we could deadlock.
2) Can't free memory with a valid mutex in it.

Separate /dev/random pseudodevice implemenation from kernel entropy pool
implementation. Rewrite pseudodevice code to use cprng_strong(9).
The new pseudodevice is cloning, so each caller gets bits from a stream
generated with its own key. Users of /dev/urandom get their generators
keyed on a "best effort" basis -- the kernel will rekey generators
whenever the entropy pool hits the high water mark -- while users of
/dev/random get their generators rekeyed every time key-length bits
are output.
The underlying cprng_strong API can use AES-256 or AES-128, but we use
AES-128 because of concerns about related-key attacks on AES-256. This
improves performance (and reduces entropy pool depletion) significantly
for users of /dev/urandom but does cause users of /dev/random to rekey
twice as often.
Also fixes various bugs (including some missing locking and a reseed-counter
overflow in the CTR_DRBG code) found while testing this.
For long reads, this generator is approximately 20 times as fast as the
old generator (dd with bs=64K yields 53MB/sec on 2Ghz Core2 instead of
2.5MB/sec) and also uses a separate mutex per instance so concurrency
is greatly improved. For reads of typical key sizes for modern
cryptosystems (16-32 bytes) performance is about the same as the old
code: a little better for 32 bytes, a little worse for 16 bytes.

First step of random number subsystem rework described in
<20111022023242.BA26F14A158@mail.netbsd.org>. This change includes
the following:
An initial cleanup and minor reorganization of the entropy pool
code in sys/dev/rnd.c and sys/dev/rndpool.c. Several bugs are
fixed. Some effort is made to accumulate entropy more quickly at
boot time.
A generic interface, "rndsink", is added, for stream generators to
request that they be re-keyed with good quality entropy from the pool
as soon as it is available.
The arc4random()/arc4randbytes() implementation in libkern is
adjusted to use the rndsink interface for rekeying, which helps
address the problem of low-quality keys at boot time.
An implementation of the FIPS 140-2 statistical tests for random
number generator quality is provided (libkern/rngtest.c). This
is based on Greg Rose's implementation from Qualcomm.
A new random stream generator, nist_ctr_drbg, is provided. It is
based on an implementation of the NIST SP800-90 CTR_DRBG by
Henric Jungheim. This generator users AES in a modified counter
mode to generate a backtracking-resistant random stream.
An abstraction layer, "cprng", is provided for in-kernel consumers
of randomness. The arc4random/arc4randbytes API is deprecated for
in-kernel use. It is replaced by "cprng_strong". The current
cprng_fast implementation wraps the existing arc4random
implementation. The current cprng_strong implementation wraps the
new CTR_DRBG implementation. Both interfaces are rekeyed from
the entropy pool automatically at intervals justifiable from best
current cryptographic practice.
In some quick tests, cprng_fast() is about the same speed as
the old arc4randbytes(), and cprng_strong() is about 20% faster
than rnd_extract_data(). Performance is expected to improve.
The AES code in src/crypto/rijndael is no longer an optional
kernel component, as it is required by cprng_strong, which is
not an optional kernel component.
The entropy pool output is subjected to the rngtest tests at
startup time; if it fails, the system will reboot. There is
approximately a 3/10000 chance of a false positive from these
tests. Entropy pool _input_ from hardware random numbers is
subjected to the rngtest tests at attach time, as well as the
FIPS continuous-output test, to detect bad or stuck hardware
RNGs; if any are detected, they are detached, but the system
continues to run.
A problem with rndctl(8) is fixed -- datastructures with
pointers in arrays are no longer passed to userspace (this
was not a security problem, but rather a major issue for
compat32). A new kernel will require a new rndctl.
The sysctl kern.arandom() and kern.urandom() nodes are hooked
up to the new generators, but the /dev/*random pseudodevices
are not, yet.
Manual pages for the new kernel interfaces are forthcoming.